Method and means for vapor cooling an electron tube



p 24, 1968 c. VAN LOO ETAL 3,402,766

METHOD AND MEANS FOR VAPOR COOLING AN ELECTRON TUBE Filed May 23, 1967 FIG. 2

INVENTORS COENRAAD VAN L00 JAMES P. POLESE BY @MBifl ATTORNEY I A United States Patent METHOD AND MEANS FOR VAPOR COOLING AN ELECTRON TUBE Cocnraad van Loo, San Jose, and James P. Polese, Menlo Park, Calitl, assignors to Varian Associates, Palo Alto, Calif., a corporation of California Filed May 23, 1967, Ser. No. 640,680 9 Claims. (Cl. 165-74) ABSTRACT OF THE DISCLOSURE Improved method and means for vapor-cooling an elec tron tube anode submersed in liquid within a boiler. Ascending vaporized liquid is restricted to a flow path closely adjacent the sides of the anode thereby increasing the velocity of ascending vapor and liquid. Replenishing liquid is introduced circumferentially about the sides of the anode into the flow path.

Background of the invention This invention relates generally to vapor-cooling systems, and particularly to improved method and means within the boilers of such systems for cooling the surface of an anode of an external anode electron tube housed therein.

Various vapor-cooling methods and means have been known and used for many years in cooling electron tubes. Early among US. patents in this field was No. 2,110,774 which, in 1938, was issued to Percy E. Privett. This work has since been continued by M. Charles Beurtheret of Saint-Germain-en-Laye, France, which has resulted in many United States patents including Numbers 2,882,446, 2,935,305, 2,935,306, 3,046,428, 3,055,643 and 3,235,004.

An anode of an external anode electron tube to be vapor-cooled is inserted through either an opening in the top or bottom of a boiler in a vapor-cooling system. The tube socket remains outside the boiler where it is available for electrical connection. The boiler is largely filled with a liquid having a high latent heat of vaporization such as water. Hereinafter this liquid will be assumed to be water, and so termed. The boiler has a conduit at or near the top for steam egress and a conduit at or near the bottom of water ingress.

When power is applied to the electron tube the anode is heated to a temperature in excess of 100 C. Water adjacent the surface of the anode vaporizes thereby liberating 540 calories of heat per gram from the anode. Vapor bubbles form on the anode and rise to the surface of the water. Unfortunately this existence of vapor bubbles at the anode surface creates a dilemma: Although this creation is the principal mechanism by which heat is liberated from the anode, the very presence of these bubbles functions as a heat dam. Consequently, it is necessary to remove vapor bubbles from the surface of the anode as quickly as possible to prevent hot spots from being created on the anode surface abutting the bubbles.

Weirs have heretofore been placed laterally about anodes decreasing the volume of the space thereabout. This decrease in volume results in an increase in the velocity of the fluids passing Within the weir adjacent the anode. Vapor bubbles are thus transported away from the surface area as they form. This however has created another problem: Where before there was an adequate supply of water located laterally about the entire length of the anode to fill space vacated by rising bubbles, now this supply is limited to the reduced lateral volume between the anode surface and the weir, and to the quantity of water which enters this reduced lateral space from the bottom open end between the anode and weir. At a cer- 3,402,766 Patented Sept. 24, 1968 tain power level the anode will become heated to such a degree that bubbles will form faster than water can rush in to replenish the vacated space. The who cannot be operated above this power level without substantial risk of self destruction or runaway through excessive heating.

Accordingly, it is an object of the present invention to provide improved method or means within the boiler of a vapor-cooling system for cooling the surface of an electron tube anode.

Another object of the invention is to provide improved method and means for removing vapor bubbles from the surface of an anode submersed in liquid within a boiler of a vapor-cooling system.

Yet another object of the present invention is to provide improved method and means for replenishing ascending water vapor adjacent the surface of an anode with additional cooling water.

Summary of the invention Briefly described the present invention relates to an improved method of cooling the anode of an external anode electron tube. The anode is submersed in a liquid having a high latent heat of vaporization and then heated to a temperature above the vaporization temperature of the liquid thereby causing liquid adjacent the anode to vaporize and ascend. The ascending vapor is restricted to a flow path closely adjacent the surface of the anode. The vaporized liquid is replenished with liquid above the bottom of the anode from a liquid flow having substantial vectoral components both normal and parallel to the surface of the anode.

This invention also relates to improved means of cooling the anode of an external anode electron tube in a vapor-cooling system adapted to be filled to a predetermined level with a liquid. The improved means comprises a boiler and a weir housed in spaced relation within the boiler defining inner and outer compartments. An anode of an external anode electron tube is housed in the inner compartment. A conduit through the weir, previous to the flow of liquid therethrough, is disposed between the bottom of the anode and the liquid level. The outlet of the conduit within the weir is disposed adjacent the anode in an upwardly facing direction rendering the conduit impervious to a flow of ascending vapor in the inner compartment.

Brief description of the drawing FIGURE 1 is a cross-sectional view of one arrangement of apparatus for vapor-cooling an anode in accordance with the method of the present invention.

FIGURE 2 is a cross-sectional view of another arrangement of apparatus for vapor-cooling an anode in accordance with the method of this invention, this arrangement being illustrated in an operative condition.

Description of the preferred embodiment Referring now in more detail to the drawing, there is shown in FIGURE 1 a cylindrical boiler 10 having a steam chest 12 forming a boiler throat 14 in one side of the steam chest. A vapor exhaust conduit 16 is connected to a boiler throat 14, and a water return conduit 18 is connected to the boiler near the bottom thereof. Conduits 16 and 18 communicate to other components of a vaporcooling system which serve to condense water vapor back to water and to maintain the level of water within boiler 10.

Housed within the boiler is a cylindrical anode 20 of an electron tube having a plurality of radially extending cooling fins 22. Socket 24 of the electron tube is located outside of boiler 10 where it is accessible for electrical connection. Surrounding anode 20 is a cylindrical weir 26 which abuts the ends of fins 22.

Boiler is filled with water to a level just below steam chest 12. This water occupies the space under anode 20, the space between anode fins 22, and the space between weir 26 and the walls of the boiler. Power is now applied 'to the electron tube causing anode and anode fins 22 to heat to a temperature in excess of the vaporization temperature of water. Water adjacent the surface of the anode and anode fins commences to vaporize thereby liberating heat from the anode. Bubbles form and grow in size until they break away from the anode surface and rise in the channels between adjacent fins to the surface of the water. The vapor enters steam chest 12 and boiler throat 14 and from there ascends through vapor exhaust conduit 16. The vapor is subsequently condensed back to liquid water and gravity fed through water return conduit 18 back into the bottom of boiler 10 thereby completing the water-vapor-water cycle.

An increase in the rate in which vapor bubbles are removed from the surface of anode 20 and anode fins 22 results in an increase in the rate of anode heat dissipation. However this is based upon the assumption that water immediately replenishes the space vacated by the removed bubbles which in turn becomes available for vaporization thus perpetuating the transfer of heat from the anode. Weir 26 serves to decrease the volume of water surrounding the anode which results in an increase in the velocity of water and water vapor flow thereabout. This increase in velocity results in an increase in the rate at which bubbles are removed from the anode surface.

Experiments have confirmed the fact that the maximum velocity is achieved where the radius of the weir has been decreased to the maximum point at which it is flush against the ends of fins 22. This optimum position, however, has in turn infringed upon the above supposition that there be adequate replenishment of the bubble space by water. Where the weir is brought into abutment with the ends of fins 22, bubbles formed all along the vertical surface of the anode must be replenished by water which is now restricted to enter the channels between adjacent fins only from the bottom thereof. This restriction limits the rate at which bubbles may be formed with adequate and timely replenishment of the space they occupy by additional water. This rate limitation in turn limits the rate of anode heat dissipation which in turn limits the power level at which the electron tube may be operated.

The method of the present invention is here used to replenish vaporized water adjacent the anode with water from a water fiow circumferentially about the anode. Conduits 28 provide the means employed by this method in FIGURE 1. These conduits pass through weir 26 thereby providing liquid communications between the reservoir of water without the weir and the water adjacent anode 20 between adjacent fins. These communications are in addition to the water entrance at the bottom of the anode and fins. Each channel between adjacent fins is provided with one conduit to service that channel. The ends of conduits 28 adjacent the anode are disposed above the ends without the weir. This arrangement prevents use of the conduits by vapor bubbles which would block replenishing water. This results in a one way inward fiow of water through the conduits.

Conduits 28 may be disposed at various angles between horizontal and vertical; however an angle of 45 is recommended. The length of the conduits without the periphery weir 26 is not significant; the length within the weir also is not critical although it is suggested that orifices be reasonably close to the surfaces of anode 20 which jbin adjacent fins since this is the locality of newly formed bubbles. For anodes operating at very high power levels and for anodes of substantial axial length, more than one deck of conduits 28 may be used. Should the anode be of the type having no fins, the circumferential locations are not limited to those between adjacent fins. Obviously, there are a host of other possible arrangements and configurations which these conduits may take. One series of tests using the configuration of FIGURE 1 in cooling an electron tube type yielding the following results.

Though the embodiment of FIGURE 1 has provided a very significant increase in the quantity of heat which may be dissipated before hot spots appear on the surface. of the anode producing runaway, and though this configuration is well suited for illustrating the principles of the present invention, it is the configuration of FIGURE 2 which is preferred in practice. A boiler 36 is shown having a steam chest 32 forming a boiler throat 34 in one side of the steam chest. A vapor exhaust conduit 36 is connected to the boiler throat, and a water return conduit 38 is connected to the boiler near the bottom thereof. Conduits 36 and 38 communicate to other components of a vapor-cooling system which serve to condense water vapor back to water and to maintain water level 40 within boiler 30 just below steam chest 32.

Housed within boiler 30 is a cylindrical anode 42 of an electron tube having a socket 44 located without the boiler confines. Flange 46 of the electron tube is secured to the top of steam chest 32 by means of O-ring 48 which is compressed by nuts and bolts thus enclosing the anode within the boiler. Seven vanes 51 in the form of holow, conical sections, are coaxially supported about anode 42 by supporting member 52. The inner edge of each vane is disposed above the outer edge. This arrangement serves to prevent vapor bubbles 54 from passing laterally through vanes 52 while providing channels through which water from without the periphery of the vanes may pass through to replenish the space vacated by rising bubbles. Vanes thus provide essentially the same functions as weir 26 and conduits 28 do in the embodiment of FIG- URE l. The embodiment of FIGURE 2 however allows a much larger and more uniform fiow of water to the surface of anode 42 from the reservoir of water located without the bounds of vanes 50. This in turn increases the heat dissipating capacity of the apparatus. As each of the inner edges of vanes 50 are located above the perspective outer edges, bubbles within the coaxially disposed set of vanes may not escape laterally between adjacent vanes. This prevents vapor from blocking the passageways between adjacent vanes which would interfere with water flowing therein. As the laterally confined vaporized water occupies many times the space of water in the liquid state, the velocity of the upward stream of water and water vapor within the weir is increased as in the embodiment of FIGURE 1.

It should be understood that the above-described embodiments are merely illustrative of applications of the principles of the invention. Obviously, many modifications may be made in the number, size, configuration and arrangement of the weir, conduits or vanes without departing from the spirit and scope of the invention as set forth in the following claims.

What is claimed is:

1. A vapor-cooling system adapted to be filled to a predetermined level with a liquid, said system comprising a boiler, a weir housed in spaced relation within said boiler defining inner and outer compartments, an anode of an external anode electron tube housed in said inner compartment, and a conduit through said weir previous to the flow of liquid therethrough disposed between the bottom of said anode and said level, said conduit having an outlet adjacent said anode and an inlet remote from said anode disposed below said outlet rendering the conduit impervious to a flow of ascending vapor from said inner compartment to said outer compartment.

2. Claim 1 wherein the peripheral surface of said anode is cylindrical and wherein said weir is supported by said electron tube in spaced relation with said peripheral surface.

3. Claim 1 wherein said anode comprises a plurality of fins and wherein said Weir abuts said fins.

4. Claim 3 having a plurality of conduits extending through said weir between said plurality of fins.

5. Claim 1 having liquid communication means adjacent the bottom of said anode defined by the bottom of said weir and the bottom of said anode.

6. Claim 1 wherein said anode and said weir are cylindrical.

7. Claim 1 having a portion of said conduit within the weir forming an acute angle with that portion of the weir located above the intersection of said conduit and weir.

8. Claim 7 wherein said angle is approximately 45.

9. A vapor-cooling system adapted to be filled to a predetermined level with a liquid, said system comprising a boiler, an anode of an external anode electron tube housed in said boiler, and a plurality of spacially separated bafiies disposed one above the other about said anode, each of said baffles having an inner edge adjacent the anode and an outer edge, and wherein the inner edge of each baflie is disposed above the outer edge thereof rendering the bafile impervious to a flow of ascending vapor therewithin.

References Cited UNITED STATES PATENTS 3,179,570 4/1965 Le F011 165181 X 3,299,949 1/1967 Beurtheret 165-185 FOREIGN PATENTS 1,034,687 4/1953 France.

213,453 3/ 1958 Australia. 1,118,235 11/1961 Germany.

969,599 9/1964 Great Britain.

ROBERT A. OLEARY, Primary Examiner.

A. W. DAVIS, Assistant Examiner. 

